The present invention relates to a high voltage gate driver IC (HVIC) and more particularly to an HVIC that includes an internal charge pumping voltage source.
FIG. 1 shows a circuit 10 that includes a voltage source VCC, a conventional HVIC 12 connected to gate terminals of high and low switches 14 and 16 connected in a half bridge. The HVIC 12 receives high and low input signals HIN and LIN and drives the high and low switches 14 and 16 by issuing control signals HO and LO to the gates of the switches 14 and 16 respectively.
The switch 14 has one terminal connected to a power supply terminal (not shown); the switch 16 has one terminal connected to the ground terminal; the other terminals of the switches 14 and 16 are interconnected at a node A. When HVICs are used in special applications, for example in a Plasma Display Panel (PDP), the node A is connected to a plurality of sustain electrodes. In the example of FIG. 1, the node A is connected to the HVIC 12.
The circuit 10 further includes a simple bootstrap circuit of a series coupled diode 18 and capacitor 20 connected between the VCC and the node A. The bootstrap circuit make a voltage source for gating. As illustrated, when the low switch 16 is ON, current from the source VCC passes the diode 18, the capacitor 20, and the low switch 16. In the circuit 10, the HVIC 12 drives the switch 16, e.g., MOSFET, whose source terminal is always connected to the ground of a constant voltage source VCC.
When HVICs are used in special applications, e.g., PDP, additional voltage sources are required. FIG. 2 shows a circuit 40 for use with a special application HVIC. The circuit 40 includes a voltage source VCC, a special application HVIC 22 connected to gate terminals of high and low switches 24 and 26. The HVIC 22 receives high and low input signals HIN and LIN and drives the high and low switches 24 and 26 by issuing control signals HO and LO to the gates of the switches 24 and 26 respectively. The switch 24 has one terminal connected to a node AH and to a first external floating voltage source VHS 32. The switch 26 has one terminal connected a node AL and to a second external floating voltage source VLS 34.
The circuit 40 further includes high and low switch capacitors 28 and 30, parallel coupled with external floating voltage sources regulators 36 and 38 respectively. One terminal of the high and low switch capacitors 28 and 30 is coupled to the node AH and AL respectively.
Accommodation of the external voltage sources 36 and 38 requires additional cost and space. The external voltage sources must have a regulator circuit or feedback system 36 and 38 for output voltage regulation. This is costly in terms of circuit space and money.
What is needed is an internal charge pumping voltage sources included in an HVIC used in circuits like PDP.